Wobbler.py

"""

This module is part of an exercise for
Think Python: an Introduction to Software Design
Allen B. Downey

"""

from swampy.TurtleWorld import *
from random import randint


class Wobbler(Turtle):
    """a Wobbler is a kind of Turtle with attributes for speed and
    clumsiness."""

    def __init__(self, world, speed=1, clumsiness=60, color='red'):
        Turtle.__init__(self, world)
        self.delay = 0
        self.speed = speed
        self.clumsiness = clumsiness
        self.color = color

        # move to the starting position
        self.pu()
        self.rt(randint(0, 360))
        self.bk(150)

    def step(self):
        """step is invoked by TurtleWorld on every Wobbler, once
        per time step."""

        self.steer()
        self.wobble()
        self.move()

    def move(self):
        """move forward in proportion to self.speed"""
        self.fd(self.speed)

    def wobble(self):
        """make a random turn in proportion to self.clumsiness"""
        dir = randint(0, self.clumsiness) - randint(0, self.clumsiness)
        self.rt(dir)

    def steer(self):
        """steer the Wobbler in the general direction it should go.
        Postcondition: the Wobbler's heading may be changed, but
        its position may not."""
        self.rt(10)


def make_world(constructor):
    # create TurtleWorld
    world = TurtleWorld()
    world.delay = .01
    world.setup_run()

    # make three Wobblers with different speed and clumsiness attributes
    colors = ['orange', 'green', 'purple']
    i = 1.0
    for color in colors:
        t = constructor(world, i, i * 30, color)
        i += 0.5

    return world


if __name__ == '__main__':
    world = make_world(Wobbler)
    world.mainloop()